1. Field of Invention
The present invention relates to an exhaust gas recirculation control apparatus and an exhaust gas recirculation control method, and more particularly, to an exhaust gas recirculation control apparatus and an exhaust gas recirculation control method using a manifold absolute pressure (MAP) sensor.
2. Description of Related Art
Exhaust gas of an engine contains a large amount of toxic ingredients, such as CO, HC, and NOx (nitrogenous compound). Particularly, when a combustion temperature of the engine increases, the amount of generation of NOx increases, so that it is necessary to lower a combustion temperature of the engine in order to reduce the amount of NOx contained in the exhaust gas.
Among the reasons of the increase of the combustion temperature of the engine, a major reason is that high temperature heat is momentarily generated according to increase of a spread speed of flames ignited in an ignition plug in a state where an air-fuel ratio of air-fuel mixed gas inside a combustion chamber is in a rich state.
A method of lowering a combustion temperature of the engine in order to reduce the amount of NOx contained in the exhaust gas includes an exhaust gas recirculation (EGR) method of lowering a combustion temperature of an engine by decreasing a density of mixed gas without changing an inherent air-fuel ratio of the mixed gas by mixing a part of exhaust gas with fresh air and making mixed gas flow in a combustion chamber.
The exhaust gas recirculation (EGR) method is used for improving fuel efficiency of a gasoline engine, as well as reducing the amount of NOx contained in the exhaust gas. By using the exhaust gas recirculation (EGR) method, it is simultaneously possible to decrease the amount of NOx and advance an ignition timing while avoiding a knocking generation region. Accordingly, it is possible to improve output of the engine and fuel efficiency.
In order to accurately control the recirculation of the exhaust gas, the amount of EGR gas recirculated to the intake manifold needs to be accurately measured. A method of measuring the amount of EGR gas includes a method of measuring a flow rate of the EGR gas by installing a flow rate sensor in an EGR pipe.
As described above, when a separate sensor is installed in order to measure the amount of EGR gas recirculated to the intake manifold, an engine configuration becomes complex and a product cost increases due to the use of an additional component.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.